Gunmen kidnapped three Westerners and killed a fourth in the historic northern Mali town of Timbuktu Friday, the second hostage-taking in the region in two days, Malian government and local sources said.

One government source and a local tourist guide identified the person who was killed as a German. The guide said two of those taken hostage were Dutch and one South African, though there was no official confirmation of their nationalities.

Thursday two French nationals were kidnapped from their hotel in the same remote desert region, where local agents for al Qaeda in the Islamic Maghreb operate.

Mohamed Ag Hamalek, a local tourist guide contacted by telephone by Reuters, described Friday's abduction. They were taking a stroll when the armed men forced them into four-wheel-drives, they shot the German dead on the spot because he tried to resist, he said.

Hamalek said the attackers sped off as security forces put up roadblocks and set off in pursuit.

The whole town is in a state of shock, because that never happened here. Most of the people in Timbuktu live off the tourism ... but already that was getting scarcer. I reckon it is finished now, he said.

Timbuktu, founded a thousand years ago and famous as a major trading centre for gold and salt, was one of the centres of a tourist sector that includes a famous festival of Malian music.

The increased risk of kidnappings, either by Islamists or by local gunmen cooperating with them, has made large tracts of Mauritania, Mali and Niger no-go areas for Westerners.

Western nations led by France and the United States are trying to improve regional cooperation, but their efforts have been undermined by a lack of resources, regional rivalries and a degree of local complicity.

There has been no claim of responsibility for either kidnapping. Al Qaeda in the Islamic Maghreb said it was behind the abduction last year of seven mine executives in neighboring Niger. Four of them remain in captivity, widely thought to be somewhere in northern Mali.

Doubts surfaced Friday over the identity of the two French nationals initially described as geologists who were kidnapped Thursday in the town of Hombori, close to the border with Burkina Faso.

France's Europe 1 radio said the two were known to French secret services. One, of Hungarian extraction, took part during the 1990s in the recruitment of Yugoslavian mercenaries to fight in then Zaire, now the Democratic Republic of Congo.

The second was arrested in September 2003 in the Indian Ocean archipelago island Comoros for his part in an attempted coup d'etat, it said.

The French Foreign Ministry declined to comment on the report, saying only it was doing all it could for their release.

(Additional reporting by Gerard Bon in Paris; Writing by Mark John; Editing by Tim Pearce)